Caenorhabditis elegans This tiny roundworm is only one millimeter long. It is ubiquitous in soil, especially near rotting vegetation.

C. elegans is so hearty that it was the only living creature to survive the Columbia space shuttle disaster. When the shuttle broke up, it was carrying more than 60 scientific experiments, with animals including bees, fish and spiders. The other animals perished, but the C. elegans were found in the rubble, swimming in their Petri dishes inside a metal locker, totally oblivious to the tragedy.May 4, 2007 http://daily.stanford.edu/article/2007/5/4/thePetriDishOrganismsToModel

Persistence of Escherichia coli O157:H7, Salmonella Newport, and Salmonella Poona in the gut of a free-living nematode, Caenorhabditis elegans, and transmission to progeny and uninfected nematodes. International Journal of Food Microbiologyl. 101:227-236.

Interpretive Summary:Foodborne illness outbreaks have raised interest in identifying pre- and postharvest sources that can contaminate raw and minimally processed fruits and vegetables. Soil that contacts produce may become contaminated with human pathogenic bacteria in a variety of ways: raw or improperly composted manure, contaminated irrigation water, runoff from pastureland, or excreta from wild animals that visit the crop areas. Higher populations of bacteria and nematodes are known to reside in the rhizosphere of plants compared to bulk soil. Free-living nematodes (microscopic worms) such as Caenorhabditis elegans are attracted to areas in soil in which large populations of bacteria are present because they feed on them, including human pathogenic bacteria. In the research reported here, we tested the hypothesis that free-living nematodes may ingest human enteric pathogens present in soil matrices and harbor them in their gut, where they could survive even after the worm dies and produce has be treated with sanitizer. Ingested pathogens may then colonize the gut and be protected against environmental stresses imposed by produce sanitizers, even after the worm has died. Worms were fed cells of E. coli OP50, E. coli O157:H7, and salmonellae then incubated at 4, 20, and 37°C for up to 5 days. Initial populations of ingested pathogens significantly increased nearly 100-fold per worm within 1 day at 20°C and remained constant for an additional 4 days. Results also show that E. coli O157:H7 and salmonellae grew from about 230 per worm to approx. 200,000 per worm and survived at least 5 days after ingestion by C. elegans. Infected worms may come into contact with pre-harvest fruits and vegetables and contaminate their surfaces by excreting pathogens. If worms on the surface of produce become attached to the surface and die, the pathogens in their gut can remain viable for several days. A strong sanitizer, 1% sodium hypochlorite, pH 13, successfully disinfected the worms and their eggs of E. coli and salmonellae Evidence also showed that worms infected with S. enterica serotype Newport could transfer this salmonellae strain to uninfected wild type , and the pathogen persisted in the gut of adult wild type C. elegans two generations removed from exposure to the pathogen. This information will help inform produce packers, scientists, and others interested in determining the mechanisms of pre-harvest produce contamination and issues of concern at post-harvest disinfection.

Technical Abstract:A study was done to determine the persistence of Escherichia coli O157:H7 and Salmonella enterica in the gut of a free-living nematode, Caenorhabditis elegans, as affected by temperature and relative humidity and to determine if infected worms transmit Salmonella enterica serotype Newport to progeny and uninfected worms. Worms were fed cells of E. coli OP50, E. coli O157:H7, and salmonellae followed by incubating at 4, 20, and 37°C for up to 5 days. Initial populations of ingested pathogens significantly increased by up to 2.93 log10 cfu/worm within 1 day at 20°C on K agar and remained constant for an additional 4 days. When plated on Bacto agar, populations of pathogens remain constant at 4°C, decreased significantly at 20°C, and increased significantly at 37°C within 3 days. Worms fed E. coli OP50 or S. enterica serotype Newport were also incubated at 4 or 20°C at relative humidities of 33, 75 or 98% for 24 h. Populations of ingested E. coli OP50 and S. enterica serotype Newport decreased by up to 1.65 and 3.44 log10 cfu/worm, respectively, in worms incubated at 20°C and 33% relative humidity for 24 h. Placement of adult worms labeled with green fluorescent protein (gfp) that had ingested gfp-labeled S. enterica serotype Newport on K agar with uninfected wild type worms resulted in transfer of the pathogen to gut of wild type worms. S. enterica serotype Newport was isolated from adult C. elegans two generations removed from exposure to the pathogen.http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=159719

II. NematodesWorms (helminths) include nematodes, cestodes, and trematodes. Nematodes are non-segmented roundworms, and the majority are free-living in the soil or water. While there are billions of nematodes that live in the soil, most (about 99%) are non-parasitic. Caenorhabditis elegans is the best known example of a nematode, free-living in soil. C. elegans is an ideal animal for genetics research, and its genome has been sequenced – it has 19,080 genes. Parasites have many more genes than their free-living counterparts because they need a wider biological arsenal to keep your immune system at bay. They live in strange places – your kidney, your lung, your brain, muscle tissue, and gut tract. All parasitic nematodes are transmitted by living close to the ground – by putting dirt in your mouth or by just stepping on the ground with your bare feet. Everybody poops and everybody eats, and parasitic nematodes take advantage of this, utilizing feces to transmit disease. In many parts of the world, fecally-contaminated water is sprayed onto vegetables as fertilizer. The vegetables are washed in contaminated water before being sold on the market. Raw produce has the potential to transmit environment-resistant stages of parasites (cooked, frozen, or peeled produce is generally safe). This may present a problem to us only when we travel to certain parts of the world, however, these parasites represent background infection for the 4 billion people today who harbor at least one species of parasitic nematode. While our immune system has methods to fight parasitic helminths, namely the eosinophil reaction (see Figure 1, courtesy of Dave Anthony), many of today’s parasites have developed ways to evade the immune response.http://healthsciences.columbia.edu/dept/ps/2007/para/old/PD1.pdf

Infection of Caenorhabditis elegans by Salmonella typhi Ty2Several serovars of Salmonella infect and kill the nematode C. elegans. However, here we report that Salmonella typhi Ty2, a representative strain of this human pathogen, readily infects the intestinal lining of C. elegans without significantly affecting its viability. Our observation suggests extending the use of the C. elegans model system for the study of host parasite relationships, to address problems concerning the biology of S. typhi.

Worming into the cell: Viral reproduction in Caenorhabditis elegans(6) in this issue of PNAS, now demonstrates that viruses that infect mammalian cells can infect, replicate, and assemble within C. elegans cells (7–9). These advances suggest that C. elegans could become an important system for understanding basic aspects of virus–host interplay.

Drugs lengthen worm's life span.By: Brownlee, Christen. Science News, 2/5/2005, Vol. 167 Issue 6, p94-94The article reports on antiseizure drugs that have been shown to increase the life span of the roundworm. A class of antiseizure drugs slows aging and increases life span in the roundworm Caenorhabditis elegans. Previous studies have identified genetic modifications that can increase the worms' life span. However, few studies have examined whether drugs might have a life-extending effect as well, says Kerry Kornfeld of the Washington University School of Medicine in Saint Louis. Kornfeld's team found that ethosuximide, an anticonvulsant drug, increased the worms' life span by 17 percent. The anticonvulsant drugs increased the worms' motility and stimulated egg laying, suggesting that the chemicals interact with C. elegans' nervous system. Reading Level (Lexile): 1390;

Share Alike.By: Barry, Patrick. Science News, 9/1/2007, Vol. 172 Issue 9, p131-131The article reports on a study conducted by scientists that reveals information about the frequency of DNA transfer from bacteria to insects and roundworms. Scientists believed that this transfer only happened occasionally, but through this series of tests, they discovered that bacteria living in the eggs of certain insects and worms can lead to a common amount of DNA swapping. This also means a higher rate of these insects acquiring new genetic traits. Reading Level (Lexile): 1270;

Survivors Extraordinaire!By: Silcox, Felicia Ann. Odyssey, Dec2004, Vol. 13 Issue 9, p28-29The article focuses on the U.S. National Aeronautics and Space Administration's (NASA's) space craft which prepared for flight in Columbia. During a last-minute check of Columbia's mid-deck section, NASA scientists found room for one more project inside a nine-pound locker. The roundworm project belonged to Catharine "Cassie" Conley, a biologist at the NASA Ames Research Center in California. Conley's goal for the worms' first space mission was simply to discover if they would be able to survive space flight when eating a new artificial food. The researcher's worms were alive, the only living things to survive Columbia's breakup. Reading Level (Lexile): 1060;